BackgroundExploratory biomarker analysis was conducted to identify factors related to the outcomes of patients with stage II-III gastric cancer using data from the Adjuvant Chemotherapy Trial of S-1 for Gastric Cancer, which was a randomized controlled study comparing the administration of an orally active combination of tegafur, gimeracil, and oteracil with surgery alone.

MethodsFormalin-fixed paraffin-embedded surgical specimens from 829 patients were retrospectively examined, and 63 genes were analyzed by quantitative real-time RT-PCR after TaqMan assay-based pre-amplification. Gene expression was normalized to the geometric mean of GAPDH, ACTB, and RPLP0 as reference genes, and categorized into low and high values based on the median. The impact of gene expression on survival was analyzed using 5-year survival data. The Benjamini and Hochberg procedure was used to control the false discovery rate.

ResultsIGF1R and AREG were most strongly correlated with overall survival, which was significantly worse in high IGF1R patients than low IGF1R patients, but better in high AREG patients than low AREG patients. The hazard ratio for death in the analysis of overall survival S-1 vs. surgery alone was reduced in the high IGF1R group compared with the low IGF1R group and in the low AREG group compared with the high AREG group. There were no significant interaction effects.

ConclusionIGF1R gene expression was associated with poor outcomes after curative resection of stage II-III gastric cancer, whereas AREG gene expression was associated with good outcomes. No significant interaction effect on survival was evident between S-1 treatment and gene expression.